KR101180205B1 - Electro-optical light modulation element, electro-optical display and modulation medium - Google Patents

Abstract

The invention relates to electrooptical light modulating elements, to electrooptical displays containing elements of this type, and to display systems, e.g. television screens and computer monitors, and to the modulating media used therein. The inventive light modulating elements contain a mesogenic modulating medium that exists in an optically isotropic phase when the light modulating elements are in operation and, in addition to having a good contrast, a low dependency on the viewing angle and very short switching times, they are particularly characterized by having relatively low driving voltages with a very low dependency on temperature. The inventive modulating media are characterized in that they contain a chiral constituent. They preferably also contain an achiral constituent. Especially preferred, the control media comprise a blue phase.

Description

ELECTRO-OPTICAL LIGHT MODULATION ELEMENT, ELECTRO-OPTICAL DISPLAY AND MODULATION MEDIUM

The present invention relates to light modulation elements, displays containing them, and light modulation media. The light modulation element preferably uses a modulation medium such as liquid crystal having anisotropy at characteristic temperature. The light modulation element is operated at a temperature at which the modulation medium is in the blue phase. A similar display using an isotropically present modulation medium is described in DE 102 17 273.0, filed September 4, 2002, and not yet published in DE 102 41 301.0, both of which are described herein. Another patent application by the applicant.

The present invention provides an electro-optical light modulation device; Electro-optic displays and display systems containing elements of this type, such as television screens and computer monitors; And a modulation medium used in the optical modulation device. The light modulation element according to the invention contains a mesogenic modulation medium which is present in the blue phase during operation of the light modulation element. In addition to good contrast and low viewing angle dependence of the contrast, short response time and relatively low operating voltage are distinguished in particular by the low temperature dependence of the operating voltage.

In particular, the invention also relates to mesogenic media and their use as modulation media in light modulation devices of this type.

Conventional electro-optical liquid crystal displays are known in general terms. It is operated at a temperature at which the modulation medium is optically present in anisotropic mesophase. In most display types, the modulation medium is used nematically. In the meso phase, the modulation medium generally has anisotropy, for example birefringence [Delta] n, without the application of an electric field. It is not induced only when an electric field is applied. TN ("twist nematic") and STN ("super twist nematic") displays are the most widely known. The liquid crystal cells of these displays have electrodes on the substrate on two opposing sides of the liquid crystal medium. Thus, the electric field is essentially perpendicular to the liquid crystal layer. In particular, the first mentioned displays are used in combination with TFTs (“thin film transistors”) that address displays of high information content and high resolution, such as displays of laptops and notebook computers. Recently, especially for desktop computer monitors, IPS ("in-plane-switching") types, such as DE 40 00 451 and EP 0 588 568) or alternatively VAN ("vertically aligned nema"). Tick ") types of liquid crystal displays have been increased. VAN displays are a variant of ECB ("electrically controlled birefringence") displays. In a modern variant of MVA ("multi-domain vertical alignment") displays, multiple domains are stabilized per addressed electrode, and special optical compensation layers are also used. These displays, such as the TN displays already mentioned, use an electric field perpendicular to the liquid crystal layer. In contrast, in contrast, IPS displays generally use electrodes only on one substrate, one side of the liquid crystal layer. That is, characterized by a significant element of the electric field parallel to the liquid crystal layer.

All existing displays have a relatively long response time. Especially in TVs and multimedia devices that are becoming more and more widespread, the reaction time is not short enough. This is particularly noticeable when compared to the ubiquitous cathode ray tube in nature. Another disadvantage of the known electro-optical effects used in liquid crystal displays is the viewing angle dependence of the contrast obtained, which is largely pronounced in most types. In most cases, this is so large that a compensation layer, typically an anisotropic film, in some cases a complex structure should be used for a display that is generally operated in direct-viewing.

DE 102 17 273.0 describes a light modulation element in which a mesogenic modulation medium is isotropic at operating temperature. These light modulation elements switch particularly fast and have a good viewing angle dependency of contrast. However, the drive voltage is too high for many applications. Thus, there is a need for improvements in light modulation devices, particularly with reduced drive voltages.

In further patent application DE 102 41 301.0, which has been unpublished by the applicant of the present invention, a special electrode structure is proposed in which the operating voltage is greatly reduced. However, these electrode structures require a great deal of work during the fabrication of light modulation elements.

The light modulation devices proposed in DE 102 17 273.0 and DE 102 41 301.0 also mention a pronounced temperature dependence. The electro-optical effect induced by the electric field in the isotropic modulation medium is most pronounced at temperatures near the clearing point of the modulation medium. This is the case when the light modulation element has the lowest feature voltage. In other words, the lowest operating voltage is required. Increasing the temperature greatly increases the characteristic voltage and thus the operating voltage. Typical temperature dependence of the threshold voltage is a few volts / ℃ to 10 volts / ℃ or more. In a first approach, according to DE 102 17 273.0 and DE 102 41 301.0 the relative temperature dependence of the characteristic voltages of the various light modulation elements containing isotropic modulation media can be considered independent of the medium of use and the electrode structure. DE 102 17 273.0 describes an isotropic medium having any of several important compositions that can be used in an optically modulated device operating in isotropic phases, while DE 102 41 301.0 discloses a variety of electrode structures. The relative temperature dependence of the threshold voltage is about 50% / ° at a temperature 1 ° above the clearing point. This drops with increasing temperature. At temperatures 5 ° above the clearing point, this is about 10% / °.

In light modulation devices used in practical displays, the temperature dependence of their electro-optical effects is usually very high. In general, it is desired that the working voltage has an effect, which is entirely independent of the working temperature over a temperature range of at least several degrees, preferably at least 5 degrees, particularly preferably at least 10 degrees, very particularly preferably at least 20 degrees. do.

Alternative development of electronics that meets drive voltage requirements is relatively complex. On the other hand, this generally results in a loss of some of the acceptable drive voltage since it must be even high enough even at the highest operating temperature. On the other hand, this also involves some measurement and control efforts. Therefore, the current temperature of the light modulation element must be measured. In displays with relatively large areas, measurement of temperature or temperature gradients at multiple points on the display may be necessary.

As such, a further alternative for keeping the temperature of the light modulation element constant cannot be easily achieved. For obvious and practical reasons, the display must be heated for this purpose. As such, this alternative requires the measurement of the temperature of the light modulation element.

The advantage of the particularly good contrast of the display described in DE 102 17 273.0 with the use of an isotropic modulation medium is not readily available in practice.

Accordingly, it can be found that there is a great demand for light modulation devices that use a modulation medium in optical isotropy and exhibit low temperature dependence of the characteristic voltage.

Liquid crystals having a correspondingly large chiral twist may have one or more optically isotropic mesophases. These phases exhibit a light blue color at a sufficiently large layer thickness, if at a corresponding cholesteric pitch, ie if the pitch is in the region of the wavelength of visible light. For this reason they are known as blue phases (see Gray and Goodby, "Smectic Liquid Crystals, Textures and Structures", Leonhard Hill, USA, Canada (1984)).

The effect of the electric field on the liquid crystal phase present in the blue phase is described, for example, in H. S. Kitzerow, "The Effect of Electric Fields on Blue Phases", Mol. Cryst. Liq. Cryst (1991), Vol. 202, pp. 51-83. Three types of blue phases (BP I to BP III) that can be observed in liquid crystals with no electric field are mentioned in this document. However, electro-optical displays using field-induced birefringence have not been described. Under the influence of the electric field, additional blue phases, or other phases other than blue phases I, II and III, may occur.

Accordingly, the present invention develops a high speed switching light modulation device having excellent contrast, good viewing angle dependence, low drive voltage and especially low temperature dependence of the drive voltage, while using a modulation medium that is optically isotropic, especially in the field-free state, The purpose is to provide the modulation medium necessary for this purpose. These light modulation elements should have a layer thickness of the smallest modulation medium possible to be suitable for use as an element of a flat panel display (FPD), for example, a flat panel screen for a computer. Moreover, they should be able to be addressed by as simple an electrode device as possible.

As described above, according to the present invention, a modulation medium in which a light modulation element using a modulation medium in an optically isotropic phase, such as the light modulation device described in the unpublished patent application DE 102 17 273.0, exists in the blue phase It has been found that it can be greatly improved by using. In particular, an optical modulation element can thus be achieved with a greatly reduced temperature dependence of the characteristic voltage and thereby a significantly reduced temperature dependence of the operating voltage.

The electro-optical light modulation device according to the present invention

At least one, preferably one or two, particularly preferably two substrates,

Electrode devices,

At least one polarizing element, and

As an electro-optical light modulation element, comprising a modulation medium;

The light modulation element is operated at a temperature at which the modulation medium in the unaddressed state is optically isotropic;

The mesogenic modulation medium comprises a chiral component (component (A)) consisting of one or more chiral compounds,

Optionally, optionally comprising an achiral component (component (B)) consisting essentially of at least one achiral compound,

The mesogenic modulation medium is operated at a temperature at which the light modulation element has a blue phase, or

The mesogenic modulation medium is operated at a temperature at which the light modulation element is isotropically,

Optionally, the electrode device is capable of generating an electric field having a significant element parallel to the surface of the mesogenic modulation medium.

It is desirable to use an electrode device capable of generating an electric field having an important component parallel to the surface of the mesogenic modulation medium.

The invention is explained in more detail below.

The modulation medium used in the light modulation element is preferably a mesogenic medium. As used herein, the term mesogenic medium or compound refers to a medium or compound having a mesophase, being soluble in the mesophase, or inducing a mesophase. The mesophase is a smectic phase, a nematic phase or a blue phase. The smectic phase and the nematic phase herein are preferably chiral. As used herein, the terms "chiral nematic phase" and "cholesteric phase" are used as synonyms unless otherwise noted. The term "blue phase" means any of the known blue phases and also includes many of these phases simultaneously unless otherwise specified.

In the application of an electric field, field-inducing phases such as BPH and BPX can occur. In the case of an electric field of high electric field strength, it is also possible for a phase transition to a phase occurring at a relatively low temperature without an electric field. Phase measurements for the characterization of materials, in particular modulation media, relate to the case where no electric field is applied, while phase measurements in the case of the characterization of light modulation elements correspond to the corresponding voltage, generally the operating voltage or threshold unless otherwise stated. It is carried out with the application of voltage. The transition temperature T ( ^* , BP) is measured in the field-absence state, while the transition temperature T (BP, I) is measured from the change in the temperature dependence increase of the characteristic voltage of the optical modulation element as the electric field is applied.

The modulation medium is preferably a blue phase, particularly preferably a blue phase and with further meso phases, preferably cholesteric phases.

The preferred medium used to investigate the mesogenic properties of materials without mesophase is nematic mixture ZLI-4792 from Merck KGaA, Darmstadt, Germany. Preferably, the mesogenic material has a clearing point of at least -50 ° C, particularly preferably at least -20 ° C, more particularly preferably at least -0 ° C, extrapolated from a 10% solution in this mixture.

The modulation medium comprises a chiral doping component (component (A)) and optionally achiral component (component (B)).

The chiral component (A) comprises one or more chiral compounds, preferably consisting of these compounds. These chiral compounds have mesogenic structures and preferably have at least one mesophase, preferably at least one cholesteric phase, per se.

In a first embodiment of the invention, the mesogenic modulation medium consists only of the chiral component (A). In this case, the modulation medium comprises at least one, preferably at least two, particularly preferably at least three, four or more chiral compounds. The modulation medium preferably comprises one or more compounds which preferably have a cholesteric phase. However, in certain embodiments, it may be advantageous that the modulation medium also includes one or more chiral compounds, one, more or all of which have no mesophase at all. In this case, chiral compounds having melting points above the ambient temperature are preferred because they can be handled more easily. Also preferred in this case are compounds having high HTP. That is, compounds that induce short cholesteric pitches, even when used at low concentrations in nematic host mixtures, are preferred.

In a particularly preferred embodiment, which may be identical to the above described embodiments, in particular the embodiments described in the last paragraph, only one or two chiral compounds, preferably only one chiral compound are used.

In a further preferred embodiment of the invention, the mesogenic modulation medium consists of a chiral component (A) and an achiral component (B). In this case, the chiral component comprises one or more, preferably two or more chiral compounds, and the achiral component (B) is one or more, preferably two or more, particularly preferably three, four or more achiral compounds It includes.

In a preferred embodiment, the chiral compound has a meso phase, preferably a cholesteric phase, or the compound of the plurality of chiral components (A) has a meso phase, preferably a cholesteric phase. In this embodiment, the chiral compound affects the physical properties of the mesogenic achiral component (B), such as its clearing point, birefringence and dielectric anisotropy (which are relatively small), and also correspondingly high concentrations of the chiral component ( A) can be used, which makes it possible to use compounds of relatively low HTP. The physical properties of the mesogenic achiral component (B), such as the clearing point, birefringence and dielectric anisotropy, change relatively little as long as the cholesteric pitch is sufficiently long and generally very large than the wavelength of light.

In another preferred embodiment, the chiral compound or chiral compound of component (A) has no mesophase. This embodiment is particularly preferred as long as the chiral component (A) has high HTP in the achiral component (B), which can be obtained by the low concentration of chiral component (A) of the desired low cholesteric pitch The result is that the physical properties of the modulation medium, such as the clearing point, birefringence and dielectric anisotropy, only slightly change compared to the achiral component (B).

However, if the cholesteric pitch in one of the two embodiments described in the two above paragraphs or in other embodiments adopts relatively low values, the chiral component (A) leads to a completely different phase in the mesogenic medium. Ie, a blue phase with a structure that is completely different from the nematic and cholesteric phases.

The physical properties of the medium, including both the chiral component (A) and the achiral component (B), such as the clear point, the birefringence and the dielectric anisotropy, generally do not allow the use of conventional methods for nematic liquid crystal mixtures. In this case, in order to measure the corresponding physical properties, the chiral component (A) is replaced with an achiral component (A ') having the same concentration. Achiral component (A ') comprises compound (s) at the same or the same concentration as component (A). However, in comparison to component (A), component (A ') does not comprise a chiral compound, but instead a corresponding chiral compound, an achiral mixture of two corresponding enantiomers each of 1: 1 of each compound. Include.

The blue phase occurs in a medium comprising both component (A) and component (B).

At least one of the achiral compounds of component (B) preferably has a meso phase, preferably a smectic and / or nematic phase, preferably a nematic phase.

In a preferred embodiment of the invention, the achiral component (B) constitutes the majority of the modulation medium. In this embodiment, the concentration of the chiral component in the modulation medium is preferably from 0.5 to 45%, particularly preferably from 1 to 35%, very particularly preferably from 3 to 25%.

In this embodiment, the cholesteric pitch of the modulation medium on the cholesteric phase, also referred to as the chiral nematic phase, can be regenerated to a first approximation by Equation 1 below.

P = (HTP? C) ^-1

Where

P is the cholesteric pitch,

c is the concentration of the chiral component (A),

HTP (helical twisting power) is a constant characterized by the twisting power of a chiral material and depends on the chiral component (A) and the achiral component (B).

If the pitch is to be measured more accurately, Equation 1 can be changed accordingly. For this reason, the expansion of the cholesteric pitch of the following formula (2) is usually used.

P = (HTP? C) ^-1 + (α ₁ ? C) ^-2 + (α ₂ ? C) ^-3 ...

Where

The parameters are as defined in Equation 1 above,

α ₁ and α ₂ are constants that vary depending on the chiral component (A) and the achiral component (B).

Equation 2 may be such that it can continuously achieve the desired accuracy.

When the chiral component (A) consists of two or more compounds, Equation 1 is changed to Equation 3 below.

P = [∑ _i (HTP (i)? C _i )] ^-1

Where

P is the cholesteric pitch,

c _i is the concentration of the i-th compound of the chiral component (A),

HTP (i) is the HTP of the i-th compound of the chiral component (A) and the achiral component (B).

The dependence of the temperature of the HTP is also represented by Equation 4, which is typically a polynomial, which can often be terminated on the right with a linear element.

HTP (T) = HTP (T ₀ ) + β ₁ ? (TT ₀ ) + β ₂ ? (TT ₀ ) ² + ...

Where

T is temperature

T ₀ is the reference temperature,

HTP (T) is HTP at temperature T,

HTP (T ₀ ) is HTP at temperature T ₀ ,

β ₁ and β ₂ are constants that vary depending on the chiral component (A) and the achiral component (B).

In a preferred embodiment of the invention, the chiral component (A) is at least 10 μm ⁻¹ , preferably at least 30 μm ⁻¹ , particularly preferred in a commercial nematic host mixture MLC-6260 from Merk Kagaea, Darmstadt. Advantageously includes at least one chiral compound having an 50㎛ ^-1 or more, very particularly preferably ^-1 or more 90㎛ HTP (helical twisting power).

In a preferred embodiment of the invention, chiral component (A) comprises two or more compounds. The chiral compounds preferably all have HTP of the same sign.

The modulation medium preferably has a characteristic temperature, in preferred embodiments a clearing point of -30 to 80 ° C, preferably up to 55 ° C.

The light modulation element according to the invention preferably contains a mesogenic medium which is present in the blue phase at the operating temperature. This medium is advantageously located above or below the substrate.

In general, the modulation medium is located between the two substrates. This embodiment is preferred. If the modulation medium is located between two substrates, one or more of these substrates are light-transmissive. The light-transmissive substrate (s) can be made of glass, quartz or plastic, for example. If a light-impermeable substrate is used, it may in particular be made of a metal or a semiconductor. These media may be used on their own or may be located on a support such as a ceramic. If the modulation medium is a polymer medium, the use of a second substrate can be omitted if necessary. The polymer modulating medium may be made self-supporting. In this case, no substrate is required. In this case, only in the case of the use of a proprietary flexible substrate, a flexible light modulation element can be achieved.

The operating temperature of the optical modulation element is preferably at least above the characteristic temperature of the modulation medium, generally at least the transition temperature of the modulation medium onto the blue phase, generally at least 0.1 to 50 ° and at least 0.1 to 10 ° above this temperature. Especially preferably, it is 0.1-5 degree or more. The operating temperature is preferably present in a range extending from the transition temperature of the modulation medium to the blue phase to the transition temperature (transparent point) of the modulation medium to the isotropic phase. However, the optical modulation element can be operated even at temperatures where the modulation medium is isotropically as described in DE 101 17 273.0. However, the temperature dependence of the operating voltage increases, which is generally undesirable.

The operating temperature range of the light modulation element according to the invention is at least preferably 5 ° or more, preferably 20 ° or more, preferably 30 ° or more, preferably 40 ° or more, particularly preferably 60 ° or more, very Especially preferably it extends beyond the temperature range of 80 degrees or more. The operating temperature range of the light modulation element according to the invention is at least preferably 10 to 50 ° C. or higher, preferably 0 to 60 ° C. or higher, particularly preferably -20 to 80 ° C. or higher, very particularly preferably -30 to At least 100 ° C, most preferably at least -40 to 120 ° C.

In a preferred embodiment, the operating temperature range of the light modulation element according to the invention compared to the characteristic temperature of the modulation medium is at least up to 50 ° C. or above, particularly preferably -5 to 60 ° C. or above, very much above the characteristic temperature. Especially preferably, it extends to -10-80 degreeC or more.

When voltage is applied, an orientation is induced in the optically isotropic mesogenic medium, which causes optical retardation, which optical delay is preferably visualized between the crossed polarisers in a known manner. Can be. Preferably a heterogeneous electric field is used.

The light modulation element according to the invention contains at least one polarizing element. In addition, they preferably contain further optical elements. This further optical element is a second polarizing element, reflector or transflector.

An optical element passes through at least one polarizing element at least once, when light passes through the mesogenic medium of the light modulation element, both before light enters the mesogenic medium and after leaving the mesogenic medium. Arranged in a manner.

In a preferred embodiment of the light modulation element according to the invention, the mesogenic medium is located between two polarizers, namely a polarizer and an analyzer. Preferably, two linear polarizers are used. In this embodiment, the absorption axis of the polarizer is preferably crossed to form a substantially 90 ° angle.

The light modulation element according to the invention optionally contains at least one birefringent layer. It preferably contains one or multiple λ / 4 wavelength layers, preferably one λ / 4 wavelength layer. The optical retardation of the λ / 4 wavelength layer is preferably about 140 nm.

The layer thickness d of the mesogenic modulation medium is preferably 0.1 to 5000 μm (ie 5 mm), particularly preferably 0.5 to 1000 μm (ie 1 mm), particularly preferably 1.0 to 100 μm, very Especially preferably, it is 1.5 micrometer, Preferably it is 3.0-30 micrometers, Especially 2.0 micrometers, Preferably it is 3.5-20 micrometers. In a preferred embodiment, the layer thickness of the mesogenic modulation medium is preferably from 0.5 to 50 μm, particularly preferably from 1.0 to 20 μm, very particularly preferably from 1.0 to 8.0 μm.

The invention also relates to an electro-optical display containing at least one light modulation element according to the invention. These electro-optical displays are preferably addressed by an active matrix.

The invention also relates to an electro-optical display system containing at least one electro-optical display according to the invention. These electro-optical display systems are preferably used as information displays, particularly preferably as television screens or computer monitors. The information displayed is preferably a digital signal or a video signal.

The light modulation element according to the present invention comprises at least one further existing optical element, such as a birefringent layer (such as a compensation layer), a dispersion layer, and an element which increases the brightness and / or light yield and / or viewing angle dependence (this list is limited May not be used).

The light modulation element according to the invention is characterized by good contrast which largely and substantially predominantly depends on the nature of the polarizer used. Compared with existing TN cells, the TN cells used herein contain an achiral liquid crystal with an optical delay of 0.50 μm, positive contrast, and an absorption axis of the polarizer perpendicular to the preferential orientation of the nematic liquid crystals in adjacent substrates. The contrast of the light modulation element of the invention depends in particular on the form, type and structure of the electrode used. If the same polarizer is used for the light modulation element according to the invention and for these conventional TN cells, the contrast of the light modulation element according to the invention is generally at least 20% in some cases more than the contrast of the TN cell, in particular significantly different from the display vertical plane. More than 40% greater than the contrast of the TN cell at the viewing angle.

The viewing angle dependence of the contrast of the light modulation element according to the present invention is very excellent. This is considerably better than known ECB cells. This is more comparable to the viewing angle dependence observed in commercially available IPS displays (e.g., Hitachi and NEC, Japan) and MVA displays (e.g., Fujitsu, Japan). This is much lower than the viewing angle dependence of conventional TN displays.

Thus, the isocontrast curve for a given contrast ratio in the light modulation device according to the invention is generally at least two times, often even three times, than the corresponding isocontrast curve for the same contrast ratio in a TN display. Includes a large angular range.

The response time of the optical modulation element according to the invention is very short. It is generally a value of 5 ms or less, preferably 1 ms or less, particularly preferably 0.5 ms or less and very particularly preferably 0.1 ms or less.

In switching between several gray shades, it is particularly advantageous that the response time, in particular the response time when switching on, is substantially independent of the drive voltage used. This represents a significant advantage over conventional light modulation devices such as liquid crystal cells, such as TN cells.

The electro-optical characteristic line is characterized by the characteristic voltage. For this reason, particularly voltages at which 10%, 50% and 90% relative contrast are reached are used. These voltages (abbreviated V ₁₀ , V ₅₀ and V ₉₀ ) are also known as threshold, mid-grey and saturation voltages, respectively. In addition, the voltage V _{70 at} which 70% relative contrast was reached was generally measured.

The electro-optical display according to the invention contains one or more light modulation elements according to the invention. In a preferred embodiment, they are addressed by the active matrix.

In another preferred embodiment, the light modulation element according to the invention is addressed in a so-called "field sequential mode". Here, the switching element is continuously illuminated with light of a different color at the same time as the addressing. For example, a color wheel, stroboscope lamp or flash lamp may be used to produce pulsed colored light.

The electro-optical display according to the invention may comprise a color filter for the display of colored images, especially when used in television screens, computer monitors and the like. This color filter advantageously consists of a mosaic of filter elements of different colors. Typically, the elements of the color filter mosaic of the color are assigned to each electro-optical switching element here.

The light modulation element according to the invention comprises an electrode structure which generates an electric field having a significant component parallel to the mesogenic medium layer. This electrode structure can be designed in the form of an interdigital electrode. It can be designed as a comb or ladder. Embodiments in the form of nested "H" and double "T" or "I" are also advantageous. The electrode structure is advantageously located on only one side of the mesogenic medium, preferably between this and the mesogenic medium using one or more substrates. The electrode structures are preferably located in two or more different planes, all located on one side of the mesogenic modulation medium. This applies in particular when the electrode structure contains very adjacent sub-structures. These sub-structures are advantageously separated from one another by a dielectric layer. If the sub-structure is located on the opposite side of the insulating layer, its placement can be chosen to enable the creation of a capacitor. This is particularly advantageous when addressing displays by active matrix. This type of active-matrix display uses a matrix of drive elements with non-linear current / voltage characteristic lines specified for individual light modulation elements such as TFT or MIM ("metal insulator metal") diodes.

The structure of a light modulation element having an optically isotropic mesogenic modulation material is described in principle in DE 101 17 273.0. The structure of the light modulation element according to the invention is briefly described herein. The switching element contains a modulation medium between the inner surfaces of the substrate. An electrode structure having two or more electrodes to which various potentials can be applied is located on the inner surface of one substrate.

The electrode may be composed of a transparent metal, such as indium tin oxide (ITO). In this case, it may be advantageous to cover part of the light modulation element using a black mask and sometimes this may be necessary. This reveals areas in which the electric field does not act so that the contrast can be improved. However, the electrode may also consist of a non-transparent material, typically a metal such as chromium, aluminum, tantalum, copper, silver or gold, preferably chromium. In this case, the use of a separate black mask may be unnecessary.

The electric field used is preferably a nonuniform electric field.

It has been found that the mutual lateral distance of the electrodes to which different potentials can be applied has a significant influence on the characteristic voltage of the color modulation element. As the distance is reduced, the required drive voltage is reduced. However, if the distance is gradually reduced, the relative pores of the light modulation element are gradually smaller, and the brightness is also reduced. The electrode is preferably 0.5 to 100 μm, preferably 1 to 20 μm, particularly preferably 1 to 15 μm, very particularly preferably 2 to 12 μm, most preferably 2 μm, preferably 3 to 11 μm. Have mutual distances in micrometers.

As the electrode distance is reduced, the driving voltage is lowered. At the same time, however, the relative porosity of the display, thereby transmitting the display, and also the brightness of the display for a given illumination is reduced. If the purpose is to optimize the brightness of the electro-optical display, an electrode distance of preferably 8 μm or more, particularly preferably 10 μm or more and very particularly preferably 12 μm or more is used. However, if the driving voltage is the main focus of the optimization, the mutual distance of the electrodes is preferably 19 µm or less, particularly preferably 15 µm or less, very particularly preferably 10 µm or less, particularly preferably 9 µm or less.

The width of the electrode in the direction of adjacent electrodes to which different potentials can be applied is less important than the distance of the electrode in its direction. This has no practical effect on the characteristic voltage of the light modulation element. However, as the width of the electrode increases, especially if the electrode is made of a material that is not transparent to light, the relative pores of the light modulation element gradually become smaller and the brightness decreases. On the other hand, as the width of the electrode decreases, its electrical resistance? Increases. The electrode preferably has a width of 0.5 to 30 μm, preferably 0.5 to 20 μm, particularly preferably 0.7 to 19 μm, very particularly preferably 1 to 9 μm and most preferably 1.5 to 6 μm.

The mesogenic medium according to the invention preferably has a blue phase. However, it is also possible to use a medium in which the temperature range of the blue phase is so narrow that practically a transition from the crystal phase, from the smetic phase or from the nematic phase to the isotropic phase occurs.

The clearing point or characteristic temperature of the mesogenic medium preferably having a blue phase is -20 to 80 ° C, preferably -30 to 80 ° C, preferably 60 ° C or less, particularly preferably 0 to 60 ° C, preferably It is preferable that it is 0-55 degreeC, Very especially preferably 20-60 degreeC, Preferably it is 50 degrees C or less. In the case of a display with a backlight, the characteristic temperature, in the preferred embodiment the transparent point, is preferably 10 to 70 ° C, particularly preferably 30 to 60 ° C.

The blue phase is preferably stable at −10 ° C. or lower, particularly preferably at −0 ° C. or lower and very particularly preferably at −40 ° C. or lower.

Optical anisotropy of the medium or optical anisotropy of the achiral component (B) of the medium is preferably at least 0.070, preferably at least 0.080, in particular at a temperature 4 ° below the characteristic temperature or clearing point of the medium or component (B) It is preferably at least 0.090, very particularly preferably at least 0.100. When using a medium having low optical anisotropy in the light modulation element according to the present invention, a high driving voltage is more essential than when using a medium having high optical anisotropy. As long as a correspondingly high driving voltage is allowed, a medium having an achiral component having optical anisotropy lower than 0.070 may also be used.

In a preferred embodiment, the achiral component (B) of the mesogenic medium according to the invention preferably has a birefringence of at least 0.100, particularly preferably at least 0.150 and very particularly preferably at least 0.200 at a temperature 4 ° below the clearing point. (Δn). In this preferred embodiment, the concentration of chiral component (A) is at most 20%, preferably at most 10% and very particularly preferably at most 7% of the mesogenic medium.

The birefringence value of component (B) is not limited to the application according to the invention. In practice, however, it is generally at most 0.500, usually at most 0.450. The birefringence value of the medium according to the invention herein is measured on the nematic phase at a temperature 4 ° below the clearing point.

Nematic mixtures of Merck Kagaa if the achiral component (component (B)) of the modulation medium is not nematically stable at this temperature, or at least it is not possible to supercool to this temperature in the nematic phase ZLI-4792 The birefringence of the mixture of the and medium is measured at 20 ° C. and extrapolated to the value of the pure medium from the change compared to the mixture ZLI-4792. 10% medium and 90% mixture ZLI-4792 is used. If the solubility of the medium is not sufficient, the concentration changes to 5%, and if the solubility thereafter is still not sufficient, then the host mixture used is the nematic mixture MLC-6828 of merk chagaea, as described in more detail below, If necessary, the concentration herein is also reduced from 10% to 5%. If the nematic phase cannot be studied at the corresponding temperature, extrapolation of values from the host mixture is used for all corresponding properties of the medium.

Component (B) of the mesogenic medium according to the invention preferably has a dipole moment of at least 4 debye, particularly preferably at least 6 debi, particularly preferably at least 8 debi.

In the optical modulation device according to the present invention, both the mesogenic modulation medium in which component B has positive dielectric anisotropy Δε and the mesogenic modulation medium in which component B has negative dielectric anisotropy can be used. . Preference is given to using mesogenic modulation media with positive dielectric anisotropy (Δε) on the mesophase.

If component (B) of the mesogenic modulation medium has positive dielectric anisotropy, it is preferably at least 15, particularly preferably at least 30, very particularly preferred at nematic phase, preferably at 1 kHz and 4 ° lower than the clearing point. It has a value of 45 or more. If the medium does not have a nematic phase of component (B) or is present as a nematic phase at a temperature 4 ° below the clearing point, its dielectric anisotropy, such as birefringence, is measured by extrapolation of the value of the corresponding host mixture. .

If component (B) of the mesogenic modulation medium has negative dielectric anisotropy, it is preferably -5 or less, particularly preferably -7 or less and very particularly preferably -10 or less. If the genetic negative component (B) or component (B) of the modulation medium is the genetic negative component, nematic mixture ZLI-3086 from Merck Kagaea is used as the host mixture if necessary.

Particular preference is given to modulation media with positive dielectric anisotropy component (B).

In the optical modulation element according to the invention the modulation medium according to the invention is, at a temperature 2 ° above the characteristic temperature, 5 to 150V, preferably 15 to 110V, particularly preferably 20 to 90V, very particularly preferably 30 It is preferred to have a characteristic voltage (V ₁₀ ) of from -80V. Unless otherwise indicated, characteristic voltages are provided in these applications for cells having an electrode width of 10 μm and an electrode distance of 10 μm. In the optical modulation element according to the invention, the modulation medium according to the invention is characterized by a property of 105 V or less, preferably 95 V or less, particularly preferably 75 V or less, and very particularly preferably 50 V or less, at a temperature 2 ° above the characteristic temperature. It is desirable to have a voltage V ₁₀ .

In a preferred embodiment of the invention, in the optical modulation element according to the invention the modulation medium according to the invention is, at a temperature 2 ° above the characteristic temperature, 2V, preferably 5 to 110V, particularly preferably 10 to 90V, Very particular preference is given to having a characteristic voltage (V ₁₀ ) of 10 to 80V.

In a further preferred embodiment of the invention, the modulation medium according to the invention in the optical modulation element according to the invention is, at a temperature 2 ° above the characteristic temperature, from 2 to 100V, preferably from 3 to 50V, particularly preferably It is preferred to have a characteristic voltage V ₁₀ of 4 to 30 V, very particularly preferably 5 to 20, most preferably 5 V or 7 to 15 V.

In this application, the characteristic temperature (T _{characteristic} ) is defined as follows.

If the characteristic voltage passes through a minimum as a function of temperature, the temperature of this minimum is referred to as the characteristic temperature.

If the characteristic voltage does not have a minimum as a function of temperature, but the modulation medium has one or more blue phases, when a large number of blue phases are produced, the transition temperature to the blue phase resulting from the rise in temperature is first called the characteristic temperature. ; If the characteristic voltage has no minimum as a function of temperature and the modulation medium does not have a blue phase, the transition temperature to the isotropic phase is referred to as the characteristic temperature.

In the optical modulation element according to the invention it is preferred that the modulation medium according to the invention has a characteristic temperature V _x of low temperature dependence, such as V ₁₀ , V ₅₀ , V ₇₀ and V ₉₀ . The temperature dependence dV _x / dT of the characteristic voltage V _x is preferably described by their relative value dV ^* _x / dT. Because of this, it is compared with each characteristic voltage at the reference temperature. The reference temperature (T _reference ) is a temperature 2 ° above the characteristic temperature of each modulation medium.

dV ^* _x / dT = dV _x (T _reference ) / dT / V _x (T _reference )

Where

V _x is the voltage at which the relative contrast of X% is achieved,

T is temperature

T _criterion represents the reference temperature, T _criterion = T _{characteristic} + 2 ° (see literature),

T _{characteristic} is characteristic temperature.

The relative temperature dependence of the characteristic voltage, preferably V ₇₀ , is preferably quoted in the range from a temperature lower than the desired operating temperature to a high temperature. The operating temperature is preferably present at 0.5 to 60 °, particularly preferably 1 to 50 ° and very particularly preferably 1 to 30 ° above the characteristic temperature of the modulation medium in the cell. For comparison of the temperature dependence of characteristic voltages, temperature dependence is referred to herein over a range from (about) 1 ° lower to (about) 1 ° higher than the characteristic temperature of the modulation medium. The temperature dependence is quoted as the difference between the voltage values at the extreme temperature (end temperature or limit temperature) and the index of the difference between these temperatures, and is specified as the average of these temperatures unless explicitly indicated otherwise.

The amount and preferably value of the characteristic voltage, preferably V _70, of the temperature dependence in this temperature range is preferably 0 to 30% / °, preferably 0 to 23% / °, preferably 22% / Or less, preferably 20% / ° or less, particularly preferably 0-15% / °, preferably 12% / ° or less, very particularly preferably 0-7% / °.

The light modulation element according to the invention preferably has a low temperature dependence over a wide range of operating temperatures.

The limiting range for temperature dependence is a temperature range of at least +/- 1 ° around the operating temperature in the selected operating temperature range from a temperature range of 2 ° above the characteristic temperature of the modulation medium to a temperature above 10 ° above the characteristic temperature, Particularly preferably an operating temperature range selected from a temperature range of +/- 4 ° or more around a temperature 5 ° above the characteristic temperature, particularly preferably from a temperature range of 2 ° above the characteristic temperature to 20 ° above the characteristic temperature It is recommended to apply over a temperature range of at least +/- 1 ° around the operating temperature, very particularly preferably over a temperature range of +/- 4 °, preferably +/- 9 ° around 10 ° above the characteristic temperature. Particularly preferred.

The modulation medium used in the optical modulation element according to the invention extends over a temperature range having a width of at least 5 °, preferably at least 10 °, particularly preferably at least 20 °, very particularly preferably at least 30 °. It is preferred to have a blue phase.

In a particularly preferred embodiment of the invention, the modulation medium used in the light modulation element according to the invention is preferably in a temperature range having a width of at least 15 °, particularly preferably at least 30 °, very particularly preferably at least 40 °. It has a blue phase extending over.

The modulation medium has an operating temperature of 20 ° C. or lower and 35 ° C. or higher, particularly preferably 10 ° C. or lower and 50 ° C. or higher, particularly preferably 0 ° C. or lower and 60 ° C. or higher, very particularly preferably -30 ° C. or lower and 80 ° C or higher. Range, preferably the blue phase.

The width of the temperature range of the blue phase is determined as follows unless explicitly stated otherwise.

First, in the liquid crystal mixture MLC-6828 commercially available from Merck Kaguea, the HTP of the individual compounds of the chiral component (A) or the entire chiral component (A) is measured.

In general, to confirm the occurrence of a blue phase, a mixture of chiral component (A) in achiral liquid crystal mixture AM-3 (specially developed for this purpose) is prepared. The composition and properties of this mixture are shown in Example 4. The concentration of component (A) in the achiral mixture is selected such that the cholesteric pitch of the resulting mixture is 180 to 800 nm, preferably 400 to 600 nm, particularly preferably 550 nm. One drop of the mixture obtained in this way is covered with a glass cover slip on the specimen slide and examined under the microscope. At layer thicknesses above about 100 μm, the blue phase can be observed directly (see Gray and Goodby in this regard).

A mixture of modulation media to be investigated can then be prepared. For this purpose, the chiral component (A) is dissolved in the achiral component (B) at a desired concentration. As an alternative to the method described above for determining the position and width of the blue phase, the starting point may be a mixture of components (A) and (B). For this purpose, the cholesteric pitch can be increased if necessary until the blue phase can be observed under the microscope. Three possibilities can be used for this, which are presented in the preferred order.

First, the concentration of component (A) is reduced by, for example, adding component (B) until the value of the cholesteric pitch indicated above in relation to the method of using reference mixture AM-3 is obtained.

Second, the HTP of component (A) is corrected by using one or more chiral compounds with HTP indications opposite to component (A) until the desired pitch is obtained.

Third, enantiomers corresponding to the compound or compounds of component (A) are used to correct the HTP of component (A) at the concentration at which the desired pitch is obtained.

A mixture of components (A) and (B) is introduced as a modulation medium into a cell having a layer thickness of 20 μm or less, preferably about 10 μm, and investigated in relation to its electro-optical properties.

The phase behavior of the modulation medium in the electro-optical test cell is then investigated. For this purpose, the temperature dependence of the characteristic voltage, preferably V ₁₀ , of the modulation medium in the reference cell according to the invention is investigated. The occurrence of a blue phase in the light modulation element is clearly seen by the onset of optical isotropy with increasing temperature. The electro-optical effect occurs at the transition temperature at which the conversion to optical isotropic phase takes place in a similar manner as described in DE 102 17 273.0. However, like the medium described in DE 102 17 273.0, the medium according to the invention is present in the blue phase and not isotropically. The characteristics of the electro-optical effect of the light modulation element according to the invention are determined as follows. The cell is (fully) dark when the polarizers intersect. This applies especially when the cholesteric pitch is much smaller than the wavelength of the light used. The contrast of the electro-optical effect according to the invention is so good that it does not have an observation angle dependence, the effect does not exhibit bistable.

As the temperature is further increased, the characteristic voltage usually increases slightly with increasing temperature. This effect can be observed over the entire range of blue phases. Even after the transition temperature from the blue phase to the isotropic phase is exceeded, the electro-optical effect can be observed. Therefore, the operating temperature range of the light modulation element according to the invention is usually larger than the range in which the blue phase occurs in the modulation medium. However, at temperatures higher than the temperature at which phase transitions from the blue phase to the isotropic phase occur, the gradient of increase in characteristic voltage with temperature is significantly greater than that of the blue phase. The interpolation from the individual (often essentially linear) curves of the characteristic voltage with temperatures below or above this transition temperature can be obtained for the transition temperature from the blue phase to the isotropic phase.

The temperature range in which the blue phase occurs in the modulation medium can also be confirmed by differential scanning calorimetry (DSC).

In the modulation medium in which the characteristic voltage of the electro-optical effect in the cell according to the invention is passed to a minimum, the difference between the two regions, which usually have different slopes (first flat and steep) of the temperature curve, can be observed. In these cases, the width of the blue phase is defined herein as follows. The upper limit temperature of the phase range is defined as the temperature at which the characteristic voltage adopts twice the minimum value of the characteristic voltage. The lower limit temperature of the phase range is defined as the temperature at which the characteristic voltage likewise adopts twice the minimum value of the characteristic voltage. However, if this value is not obtained at a temperature below the minimum temperature, the temperature at which the electro-optical effect first appears with increasing temperature is defined as the lower limit temperature of the phase range.

Electro-optical when viewing at a preferred viewing angle over a viewing angle range extending horizontally and vertically to at least 30 °, preferably at least 40 °, particularly preferably at least 45 °, very particularly preferably at least 60 ° The effect exhibits a contrast ratio of at least 5: 1, more preferably at least 10: 1 and very particularly preferably at least 15: 1.

The electro-optical effect preferably exhibits a response time of 15 ms or less, preferably 10 ms or less, particularly preferably 5 ms or less, and very particularly preferably 3 ms or less. Response time throughout this application is determined under the following conditions, unless expressly stated otherwise. Once the switch-on time (τ _on ) is determined, the value of the rectangular voltage is increased from V ₀ to V ₁₀₀ of the switching element and the time taken for a 10% to 90% transition or relative contrast change is measured. . The switch-off time τ _off is quoted for the relative contrast switching from 90% to 10% while reducing the voltage from V ₁₀₀ to V ₀ .

If the transparent point of the modulation medium in the cell is different from the bulk case, at a characteristic voltage at which the modulation medium does not have a blue phase and does not pass the minimum value, the temperature is based on the transparent point of the cell.

If the mesogenic modulation medium does not have a clear transparent point, but has a relatively wide transparent point range (typically a few degrees wide) when measured in the capillary of a transparent point measuring instrument (Mettler), in this case The transparent point of is not defined as the start of the range of transparent points as opposed to the conventional definition but instead is defined as the end point of the range of transparent points.

The mesogenic medium according to the invention preferably consists of 2 to 40 compounds, particularly preferably 5 to 30 compounds, very particularly preferably 7 to 25 compounds.

The chiral compound of the chiral component (A) preferably has a high HTP. They are also referred to as chiral dopants because they are added to the mesogenic base mixture at relatively low concentrations. They preferably have good solubility in the achiral component (B). As long as the cholesteric pitch has a value much smaller than the wavelength of the light, they do not impair the mesogenic or liquid crystalline properties of the mesogenic medium or only to a small extent. However, when the cholesteric pitch is at the wavelength level of light, they induce a blue phase having a structure that is completely different from the cholesteric phase. When using two or more chiral compounds, they may have the same or opposite direction of rotation and the temperature dependence of the same or opposite twists.

Merck kage ah chiral compounds having 20㎛ ^-1 or more, and particularly 40㎛ ^-1 or more, and particularly preferably ^-1 or more 70㎛ HTP in the liquid crystal mixture MLC-6828 which is commercially available from are particularly preferred.

In a preferred embodiment of the invention, the chiral component (A) consists of two or more chiral compounds, all with the same indication of HTP.

The temperature dependence of HTP of individual compounds may be high or low. By mixing compounds having different temperature dependencies of HTP in corresponding ratios, the temperature dependence of the pitch of the medium can be corrected.

In the case of optically active ingredients, those skilled in the art will appreciate that many chiral dopants, some of which are commercially available, such as cholesteryl nonanoate, R / S-811, R / S-1011, R / S-2011, R / S-3011, R / S-4011, B (OC) 2C ^* HC-3 or CB15 (all from Merck Kaaea, Darmstadt) can be used.

Particularly suitable dopants are compounds containing at least one chiral radical and at least one mesogenic group, or at least one aromatic or cycloaliphatic group which forms together with the chiral radical a mesogenic group.

Suitable chiral radicals are, for example, chiral branched hydrocarbon radicals, chiral etinadiols, binaphthol or dioxolane, also sugar derivatives, sugar alcohols, sugar acids, lactic acid, chiral substituted glycols, steroid derivatives, terpene derivatives, amino acids or Monovalent or polyvalent chiral radicals selected from the group consisting of several, preferably one to five amino acid sequences.

Preferred chiral radicals are sugar derivatives such as glucose, mannose, galactose, fructose, arabinose, dextrose; Sugar alcohols such as sorbitol, mannitol, iditol, galactitol or their anhydrous derivatives, in particular dianhydrosorbide (1,4: 3,6- dianhydro-D-sorbide, isosorbide), dianhydro Dianhydrohexitols such as mannitol (isosolbitol) or dianhydro iditol (isoiditol); Sugar acids such as gluconic acid, gulonic acid, ketogulonic acid; Chiral substituted glycol radicals, such as mono- or oligoethylene or propylene glycol, wherein at least one CH ₂ group is substituted by alkyl or alkoxy; Amino acids such as alanine, valine, phenylglycine or phenylalanine, or sequences of one to five of these amino acids; Steroid derivatives such as cholesteryl or cholic acid radicals; Terpene derivatives, for example menthyl, neomentyl, campanile, pinale, terpineyl, isolongipolyl, pentyl, caryle, myrtenyl, nofil, geraniyl, linalyl, neryl, citronellol or Dihydrocitronellol.

Suitable chiral radicals and mesogenic chiral compounds are for example DE 34 25 503, DE 35 34 777, DE 35 34 778, DE 35 34 779 and DE 35 34 780, DE 43 42 280, EP 01 038 941 and DE 195 41 820.

Particular preference is given to dopants selected from the group consisting of compounds of the formulas A-I to A-III.

Where

R ^a11 and R ^a12 are independently of each other alkyl, oxaalkyl or alkenyl having 2 to 9, preferably up to 7 C atoms, and R ^a11 is alternatively methyl or alkoxy having 1 to 9 C atoms Preferably both are alkyl, preferably n-alkyl;

R ^a21 and R ^a22 are each independently of the other alkyl or alkoxy having 1 to 9, preferably 7 or less C atoms; Oxaalkyl, alkenyl or alkenyloxy having 2 to 9, preferably up to 7 C atoms, preferably both are alkyl, preferably n-alkyl;

R ^a31 and R ^a32 are independently of each other alkyl, oxaalkyl or alkenyl having 2 to 9, preferably up to 7 C atoms, and R ^a31 is alternatively methyl or alkoxy having 1 to 9 C atoms And preferably both are alkyl, preferably n-alkyl.

Particular preference is given to dopants selected from the group consisting of compounds of the formulas A-I-1, A-II-1 and A-III-1.

Other preferred dopants are derivatives of isosorbide, isomannitol or isoditol of formula A-IV, and for example diphenylethanediol (hydrobenzoin), in particular mesogenic hydrobenzoin derivatives of formula AV (not shown) Chiral etindadiols such as (R, S), (S, R), (R, R) and (S, S) enantiomers).

Where

는

(다이안하이드로솔비톨),

(다이안하이드로만니톨) 또는

(다이안하이드로아이디톨), 바람직하게는 다이안하이드로솔비톨이고;group

The

(Dianhydrosorbitol),

(Dianhydromannitol) or

(Dianhydroiditol), preferably dianhydrosorbitol;

B and C are each independently 1,4-phenylene which may be mono-, di- or tri-substituted by L or 1,4-cyclohexylene;

L is H, F, Cl, CN or alkyl, alkoxy, alkylcarbonyl, alkoxycarbonyl or alkoxycarbonyloxy having 1 to 7 C atoms optionally halogenated;

c is 0 or 1;

Z ⁰ is —COO—, —OCO—, —CH ₂ CH ₂ — or a single bond;

R ⁰ is alkyl, alkoxy, alkylcarbonyl, alkoxycarbonyl or alkylcarbonyloxy having 1 to 12 C atoms.

Compounds of formula A-IV are described in WO 98/00 428. Compounds of formula A-V are described in GB-A-2,328,207.

Very particularly preferred dopants are chiral binaphthyl derivatives described in WO 02/94 805, chiral bainaphthol acetal derivatives described in WO 02/34 739, chiral TADDOL derivatives described in WO 02/06 265. And chiral dopants containing one or more fluorinated crosslinking groups and terminal or central giral groups described in WO 02/06 196 and WO 02/06 195.

Especially preferred are chiral compounds of the formula A-VI.

Where

X ¹ , X ² , Y ¹ and Y ² are each independently of each other F, Cl, Br, I, CN, SCN, SF ₅ ; By F, Cl, Br, I or CN, or is substituted one to be replaced, and also how to prevent one or more non-adjacent CH ₂ groups are not bonded to each other, each independently, O and / or S atoms are directly to each other -O-, - S-, -NH-, NR ^0- , -CO-, -COO-, -OCO-, -OCOO-, -S-CO-, -CO-S-, -CH = CH- or -C≡C- Straight or branched chain alkyl having 1 to 25 C atoms, which may be replaced by; Polymerizable groups; Or cycloalkyl or aryl having up to 20 C atoms, which may be optionally mono- or polysubstituted by halogen, preferably F, or a polymerizable group;

R ⁰ is H or alkyl having 1 to 4 C atoms;

x ¹ and x ² are each independently 0, 1 or 2;

y ¹ and y ² are each independently 0, 1, 2, 3 or 4;

B ¹ and B ² are each independently an aromatic or partially or fully saturated aliphatic 6 membered ring in which one or more CH groups can be replaced with N atoms and one or more non-adjacent CH ₂ groups can be replaced with O and / or S;

는

또는

이며;W ¹ and W ² are each independently of each other —Z ¹ -A ^1- (Z ² -A ² ) _m -R, one of which is alternatively R ¹ or A ³ , but not both at the same time, or

The

or

;

U ¹ and U ² are each independently of each other CH ₂ , O, S, CO or CS;

가

인 경우에는 둘 다가 단일 결합을 나타낸다.V ¹ and V ² are each (CH ₂ ) _n , _wherein 1 to 4 CH ₂ groups that are not adjacent to each other may be replaced with O and / or S, one of V ¹ and V ² , and

end

In which both represent a single bond.

Z ¹ and Z ² are each independently of each other -O-, -S-, -CO-, -COO-, -OCO-, -O-COO-, -CO-NR ^0- , -NR ⁰ -CO-, -O-CH _2- , -CH ₂ -O-, -S-CH _2- , -CH ₂ -S-, -CF ₂ -O-, -O-CF _2- , -CF ₂ -S-,- S-CF _2- , -CH ₂ -CH _2- , -CF ₂ -CH _2- , -CH ₂ -CF _2- , -CF ₂ -CF _2- , -CH = N-, -N = CH-, -N = N-, -CH = CH-, -CF = CH-, -CH = CF-, -CF = CF-, -C≡C-, any O and / or S and / or N atoms are directly A combination of two of these groups, preferably —CH═CH—COO— or —COO—CH═CH—, or a single bond so as not to be bound;

A ¹ , A ² and A ³ are each independently of one another 1,4-phenylene, in which one or two non-contiguous CH groups can be replaced by N, and one or two non-contiguous CH ₂ groups are O and / or S 1,4-cyclohexylene, 1,3-dioxolane-4,5-diyl, 1,4-cyclohexenylene, 1,4-bicyclo [2.2.2] octylene, which may be substituted by Piperidine-1,4-diyl, naphthalene-2,6-diyl, decahydronaphthalene-2,6-diyl or 1,2,3,4-tetrahydro-naphthalene-2,6-diyl Each of these groups may be mono- or polysubstituted by L, and A ¹ is a single bond;

L is a halogen atom, preferably F; CN, NO ₂ ; One or more H atoms is alkyl, alkoxy, alkylcarbonyl, alkoxycarbonyl or alkoxycarbonyloxy having 1 to 7 C atoms, which may be replaced by F or Cl;

m is independently at each occurrence 0, 1, 2 or 3;

R and R ¹ are each independently of each other H, F, Cl, Br, I, CN, SCN, SF ₅ ; Optionally mono- or polysubstituted by F, Cl, Br, I and CN and at least one non-adjacent CH ₂ group is -O-, -S-, so that two O and / or S atoms are not directly bonded to each other, -NH-, -NR ^0- , -CO-, -COO-, -OCO-, -O-COO-, -S-CO-, -CO-S-, -CH = CH- or -C≡C- Straight or branched alkyl each having 1 or 3 to 25 C atoms, which can be replaced with; Or a polymerizable group.

Especially preferred are chiral binaphthyl derivatives of the formulas A-VI-1, in particular compounds selected from the formulas A-VI-1a to A-VI-1c.

Where

B, R ⁰ and Z ⁰ are as defined for Formula A-IV,

b is 0, 1 or 2,

Z ⁰ is in particular -OCO- or a single bond.

Also particularly preferred are chiral binaphthyl derivatives of formula A-VI-2, in particular compounds selected from formulas A-VI-2a to A-VI-2f.

Where

R ⁰ is as defined for Formula A-IV,

X is H, F, Cl, CN or R ⁰ , preferably F.

In particular, the dopants of the formulas A-IV, AV and A-VI, in particular A-VI-1a to A-VI-1c and A-VI-2a to A-VI-2d, exhibit good solubility in the achiral component, Induces cholesteryl structure with high twist dependence and low temperature dependence of spiral pitch. Thus, even if only one of these dopants is used in small amounts, it is possible to obtain a medium according to the present invention with desirable properties, in particular suitable for use in light modulation elements in which the modulation medium is addressed on optical isotropy.

The achiral component (B) of the mesogenic medium according to the invention having positive dielectric anisotropy according to the invention preferably comprises the following components.

Component (B-A) consisting of at least 30 compounds having at least 30 very strong positive dielectric anisotropies;

Optionally a component (B-B) consisting of one or more compounds having a strong positive dielectric anisotropy of 10 to <30;

Optionally a component (B-C) consisting of one or more compounds having a medium positive dielectric anisotropy of> 1.5 to <10;

Optionally a component (B-D) consisting of a compound which is neutral in at least one dielectric aspect with a dielectric anisotropy of -1.5 to +1.5; And

Optionally a component (B-E) consisting of one or more compounds having a negative dielectric anisotropy of less than -1.5.

Component (BA) of component (B) of these media preferably comprises at least one compound of formula (I), particularly preferably consisting mainly of at least one compound selected from compounds of formula (I) and formula (II), Very particularly preferably consists essentially of one or more compounds selected from these compounds.

Where

R ¹ is alkyl having 1 to 7, preferably 2 to 5 C atoms, oxaalkyl having 2 to 7, preferably 2 to 5 C atoms, preferably alkyl;

는

이고;

The

ego;

Z ¹¹ and Z ¹² are each independently a single bond, -CO-O-, trans-CH = CH-, -CH = CF-, -CF = CH-, -CF = CF-, -CH = CH-CO -O-, -CF = CF-CO-O-, -CF = CH-CO-O-, -CH = CF-CO-O-, -CF ₂ -O-, -O-CF ₂ -or -C ≡C-, or a combination of two or more of these groups, preferably one or more of these groups is -COO- or -CF ₂ -O-;

X ¹ is F, -OCF ₃ , -CF ₃ , -OCF ₂ H, Cl, CN, -C≡C-CN or NCS, preferably CN, -CF ₃ , -C≡C-CN or NCS, in particular Preferably CN or -CF ₃ ;

Y ¹¹ , Y ¹² , Y ¹³ and Y ¹⁴ are H or F;

n ¹ is 0 or 1, preferably 0;

The compounds of formula (I) preferably have at least 3, particularly preferably at least 4, fluorine atoms on the phenyl ring, but preferably up to 2 F atoms per 1 phenyl ring, Y ¹¹ , Y ¹² and Y ¹³ is particularly preferably F and Z ¹² is preferably -COO-;

R ² is alkyl or alkoxy having 1 to 7 C atoms; Alkenyl, alkenyloxy or oxaalkyl having 2 to 7 C atoms, preferably alkyl or alkoxy having 1 to 5 C atoms, or alkenyl having 2 to 5 C atoms, preferably alkyl or Alkoxy;

는

이고;

The

ego;

Z ²¹ and Z ²² are each independently a single bond, -CO-O-, trans-CH = CH-, -CH = CF-, -CF = CH-, -CF = CF-, -CH = CH-CO -O-, -CF = CF-CO-O-, -CF = CH-CO-O-, -CH = CF-CO-O-, -CF ₂ -O-, -O-CF ₂ -or -C ≡C-, or a combination of two or more of these groups, preferably one or more of these groups is -COO- or -CF ₂ -O-;

X ² is F, -OCF ₃ , -CF ₃ , -OCF ₂ H, Cl, CN, -C≡C-CN or NCS, preferably CN, -CF ₃ , -C≡C-CN or NCS, in particular Preferably CN;

Y ² is H or F,

n ² is 0 or 1.

In a preferred embodiment herein, component (B) of the medium comprises at least one compound of formula (I), preferably consists mainly of at least one compound of formula (I), particularly preferably essentially at least one compound of formula (I) It consists only of.

The compound of formula I is preferably selected from the group consisting of the compounds of formulas I-1 and I-2.

Where

The variables are as defined above for Formula I, preferably

R ¹ is alkyl having 1 to 7, preferably 1 to 5, preferably up to 3 C atoms,

Z ¹² is -COO- or -CF ₂ -O-,

X ¹ is CN, —CF ₃ or NCS, preferably CN or —CF ₃ .

The medium according to the invention particularly preferably comprises at least one compound of formula (I), preferably a compound of formula (I-1 and / or I-2), wherein X ¹ is CF ₃ .

The compound of formula II is preferably selected from the group consisting of the compounds of formulas II-1 to II-7.

Where

The variables are as defined above for Formula II, preferably

R ² is alkyl or alkoxy having 1 to 7 C atoms; Alkenyl, alkenyloxy or oxaalkyl having 2 to 7 C atoms, preferably alkyl or alkoxy having 1 to 5 C atoms,

Z ²² is a single bond, -CO-O- or -CF ₂ -O-, preferably -COO- or -CF ₂ -O-, particularly preferably in formula II-6, -C≡C-,

X ² is CN or CF _3, preferably CF _3, and, in formula II-6, particularly preferably CN or CF _3, preferably CN.

The media according to the invention preferably comprise at least one compound selected from the group consisting of compounds of the formulas II-1 to II-5, preferably compounds wherein Z ²² is -CO-O- or -CF ₃ -O- do.

In a preferred embodiment of the invention, component (BA) of component (B) of the medium according to the invention preferably comprises at least one compound of formula (II), particularly preferably consisting mainly of at least one compound of formula (II) And very particularly preferably consists essentially of at least one compound of the formula (II).

In the case of the optical modulation device according to the present invention, both mesogenic modulation medium with positive dielectric anisotropy (Δε) and mesogenic modulation medium with negative dielectric anisotropy can be used. Preference is given to using mesogenic modulation media with positive dielectric anisotropy (Δε) on the mesophase. If the mesogenic modulation media have positive dielectric anisotropy, the achiral component (B) of these media is at 1 kHz and at 4 ° below the clearing point, preferably on the nematic phase, preferably at least 40, particularly preferably It has a Δε value of at least 50, very particularly at least 60.

Component (B) of the mesogenic medium according to the invention, having positive dielectric anisotropy, is particularly preferably composed mainly of component (B-A) and very particularly preferably consists essentially of component (B-A).

In a preferred embodiment, component (B) of the mesogenic medium according to the invention, having positive dielectric anisotropy, is selected from the group consisting of components (BB) to (BD), preferably components (BB) and (BD) At least one component selected from the group consisting of, particularly preferably component (BB).

Component (B) of the mesogenic medium according to the invention, having positive dielectric anisotropy, preferably comprises:

5 to 80%, preferably 10 to 60%, particularly preferably 18 to 43% of at least one compound of the formula (I),

5 to 95%, preferably 15 to 80%, particularly preferably 40 to 70%, of at least one compound of formula II, and

0-30% of one or more additional compounds, preferably 0-15%, particularly preferably 0-10%.

Component (B) of the mesogenic medium according to the invention, having positive dielectric anisotropy, preferably comprises:

3 to 45%, preferably 5 to 40%, particularly preferably 10 to 35%, and / or one or more compounds of formula (I-1)

2 to 35%, preferably 4 to 30%, particularly preferably 5 to 30%, and / or one or more compounds of formula (I-1)

0-30%, preferably 2-25%, particularly preferably 5-20%, and / or one or more compounds of formula II-1

0-30%, preferably 2-25%, particularly preferably 5-20%, and / or one or more compounds of formula II-2

5 to 70%, preferably 15 to 65%, particularly preferably 20 to 60%, and / or one or more compounds of formulas II-3 and / or II-4, preferably II-4

0-20%, preferably 0-15%, particularly preferably 3-12%, and / or one or more compounds of formula II-5

0-30%, preferably 0-20%, particularly preferably 3-15%, and / or one or more compounds of formula II-6

0 to 35%, preferably 0 to 30%, particularly preferably 3 to 12%, of at least one compound of the formula II-7.

The component (B) of the mesogenic medium according to the invention with negative dielectric anisotropy is particularly preferably composed mainly of component (B-E) and very particularly preferably consists essentially of component (B-E).

Component (B-E) of these media preferably comprises one or more compounds.

Mesogenic media with negative dielectric anisotropy according to the invention preferably comprise:

A component (B-A ') consisting of one or more compounds having a strong negative dielectric anisotropy of -5 or less,

Optionally, a component (B-B ') consisting of one or more compounds having a medium negative dielectric anisotropy of -1.5 to <5,

Optionally a component (B-C ′) consisting of a compound which is neutral in at least one dielectric aspect with a dielectric anisotropy of -1.5 to +1.5, and

Optionally a component (B-D ′) consisting of one or more compounds having a positive dielectric anisotropy greater than 1.5.

Mesogenic media according to the present application preferably include:

At least 4, preferably at least 6 compounds and / or selected from the group consisting of compounds of components (A) and (B)

At least 5 of the compounds of component (B) and / or

One, two or more of the compounds of component (A).

The mesogenic media according to the invention may comprise further additives such as stabilizers or dichroic dyes in customary concentrations. The total concentration of these additional components is 0 to 10%, preferably 0.1 to 6%, based on the total mixture. The concentration of the individual compounds among them is preferably 0.1 to 3%. Unless expressly stated to the contrary, the concentrations of these compounds and similar components in the mixture are not taken into account when indicating the concentration range of the remaining mixture components.

The medium is obtained from the compound in a conventional manner. Compounds used in smaller amounts are advantageously dissolved in compounds used in larger amounts. If the temperature rises above the clearing point of the main component during the mixing process, it is readily apparent that dissolution is complete. However, the media according to the invention may also be produced in different ways, for example through the use of premixes. Premixes which can be used are themselves homogeneous mixtures and / or eutectic mixtures. However, the premix may also be a medium already available on its own. This is the case for so-called two bottles or multiple bottle systems.

Unless expressly stated otherwise, the following applies herein.

The range of values mentioned preferably includes limits.

Concentrations are expressed in weight percent and are based on the entire mixture. The temperature is expressed in degrees Celsius, and the temperature difference is expressed in degrees Celsius. All physical properties were measured as described in "Merck Liquid Crystals, Physical Properties of Liquid Crystals", November 1997, Merck KGaA, Germany, and are values for temperatures of 20 ° C unless explicitly stated otherwise. Is displayed. Optical anisotropy (Δn), also known as birefringence, is measured at a wavelength of 589.3 nm. Dielectric properties are measured at a frequency of 1 kHz. The properties of the mesogenic modulation media, in particular their achiral components (B), are measured at a temperature 4 ° below each clearing point.

The cholesteric pitch of cholesteric medium or chiral nematic medium is measured by known methods depending on its size.

In the case of relatively large values, it is measured by the Grandjean-Cano method. To this end, the material introduces the material into a thermostated wedge-shaped cell uniformly arranged on a substrate. Determine the spacing of the disclination lines observed and calculate the pitch through the angle of the wedge. The wedge angle used depends on the pitch to be determined. Cells with wedge angles of about 0.1 to 4 degrees, preferably 0.5 to 3 degrees, particularly preferably 0.1 to 2 degrees are typically used. The spacing of the revolving lines is preferably measured under a microscope. Orientation deficiency is considered by averaging the values correspondingly. Alternatively, the average of the intervals can be determined by diffraction of a laser beam (eg, He-Ne laser) in the grating of the revolving line. The maximum diffraction here is advantageously measured by a diode array or CCD. The angle of the wedge cell is preferably determined by the multiple reflections of the laser beam. Alternatively, this can be obtained by adjusting the measurements by the outer shape of the cell or by using a material of known pitch. Measurement accuracy for pitch is about +/- 1% to about +/- 3% depending on the measurement method and the current value.

If the pitch value is too large, the lens method is used. Here, the material is oriented between the flat plate and the convex lens. Next, the spacing of the annular rotation line is measured. This can be done using an image processing system that simplifies the averaging of the data. The distance of the lens surface from the planar substrate at the position of the revolving line is obtained from the radius of the lens and the distance of the revolving line from the contact point. The measurement accuracy of this method is somewhat lower than that of using wedge cells, but can cover a wide range of pitch values.

Very small pitch values are determined using an optional reflection method. To this end, the transmission through the oriented sample of material is determined. The pitch is obtained from the maximum wavelength of the selective reflection by the refractive index of the material. In this method, the measurement accuracy for pitch is likewise about +/- 1%.

By the GrandZine-Kano method, the HTP of chiral materials, in particular individual chiral compounds, is determined according to the application at 20 ° C. in a nematic host mixture MLC-6828, available from Merk Kagaea, Darmstadt. The temperature dependence of HTP in the range of 0-50 ° C. is investigated and is typically quoted at 20 ° C. In general, HTP is also determined in the nematic host mixture MLC-6260, which is commercially available from Merck Kagaea.

If the cholesteric pitch of the modulation medium cannot be determined, it is estimated from the HTP of component (A) in component (B). Even if the value of HTP of component (A) in component (B) cannot be determined at the corresponding temperature, this is estimated, but in this case it is usually estimated from the temperature dependence of HTP at lower temperatures.

With respect to the details of the composition of the medium or its components, "comprises" means in each case the concentration of said substance, i.e. component or compound, in the reference unit, i.e. Preferably at least 20%, very particularly preferably at least 30%; "Consisting mainly" means that the concentration of said substance in the reference unit is preferably at least 50%, particularly preferably at least 60%, very particularly preferably at least 70%; “Essentially consists only of it” means that the concentration of said substance in the reference unit is preferably at least 80%, particularly preferably at least 90%, very particularly preferably at least 95%.

Compounds positive in dielectricity have a Δε of> 1.5, compounds neutral in dielectricity have a Δε of −1.5 < Δ < ε < 1.5, and compounds negative in dielectricity have a Δε of <-1.5. The same definition applies to the components or mixtures of mixtures.

Dielectric properties, electro-optical properties (such as threshold voltages) and response times were determined in test cells produced at Mert Cagea, Darmstadt, Germany. The test cell, which determines Δ 가, had a ring ring and a protective ring of indium tin oxide (ITO) having a layer thickness of 22 μm and an area of 1.13 cm 2. ε _? For homeotropic orientation to determine the cell with the polyimide alignment layer homeotropically oriented was used. Alternatively, lecithin (mert chagaea) can be used as the alignment agent. The cell for determining ε _을 had an orientation layer of polyimide AL-1054 from Japan Synthetic Rubber, Japan. Capacitance was typically measured using a Solatron 1260 frequency analyzer with square wave and effective voltage of 0.3V _rms . For materials with high dielectric anisotropy, where the liquid crystal director has already been _{redirected at} a voltage of 0.3 V _rms , a lower voltage of 0.1 V _rms is used in particular. Electro-optic irradiation was performed using white light. The characteristic voltage was determined by vertical observation.

At a frequency of 1 kHz and possibly 20 ° C., and at 4 ° below the transition temperature to the optical isotropic phase (blue phase or isotropic phase) which first occurs with increasing temperature, and 4 ° below the clearing point or characteristic temperature of a particular material. At high temperatures, the dielectric properties of the material are preferably determined.

The dielectric anisotropy (Δε) of the compounds is determined by extrapolating the value of a 10% solution of the individual compounds in a host mixture at 20 ° C. to a proportion of 100% of the individual compounds. The capacitance of the test mixture is determined in both cells with homeotropic boundary orientation and cells with horizontal boundary orientation. The layer thickness of both cell types is about 20 μm. Measurements are made using square waves with an effective voltage (rms, mean of squares) of 1 kHz and typically 0.1 V or 0.2 V to 1.0 V. In each case, the voltage used is lower in each case than the capacitance threshold of the mixture to be irradiated.

For compounds that are positive in dielectric terms, the mixture ZLI-4792 is used as the host mixture, and for compounds that are neutral in dielectric and negative compounds in the dielectric, the mixture ZLI-3086 is used as the host mixture. Are all made in Germany by Merck Kagaea. These host mixtures are used for components and media that do not have a nematic phase at appropriate temperatures or cannot be subcooled to an appropriate temperature in the nematic phase. If the solubility of the compound, component or medium in the individual host mixture is less than 10%, the concentration of the component to be investigated is particularly reduced to 5%. If the solubility of a positive component (compound, component of the medium, or medium) in the host mixture ZLI-4792 is less than 5%, the nematic mixture MLC-6828 from Merck Kagaea, Germany, is used as the host mixture. do. Here too, the concentration of the component to be irradiated is halved from 10% to 5%, if necessary. The value of the pure component is extrapolated from the change in value compared to the value of the host mixture.

The medium according to the invention preferably comprises 0 to 10% of a compound having a solubility of less than 5% in the corresponding host mixture (ZLI-3086 or MLC-6828). The concentration of these compounds is preferably at most 8%, particularly preferably at most 5% and very particularly preferably at most 4%.

The dielectric anisotropy of the compound, component or medium that is not nematic phase or cannot be subcooled to this temperature at 20 ° C. or at a temperature 4 ° below the clearing point is determined from the host mixture as described above in the case of compounds. .

Dielectric constant ε _{? With} absolute accuracy of about +/- 0.1 to +/- 0.2 And ε _⊥ , the accuracy providing an absolute accuracy of about +/- 0.2 to +/- 0.4, typically +/- 0.3, for dielectric anisotropy (Δε). The higher the accuracy, the lower the accuracy. That is, the possible deviation increases. The absolute accuracy is about +/- 0.5 at values of Δε of 25 to 40, and the absolute accuracy is about +/- 1.0 at values greater than 40.

Determine the dielectric susceptibility of the medium at a temperature 4 ° above the characteristic temperature. This is referred to as the average dielectric loss (ε _mean ) because it may be obtained as a first approach value from extrapolation of the average dielectric loss of the nematic medium above the clearing point. The dielectric susceptibility of the medium is determined with an absolute accuracy of about +/- 0.1 to +/- 0.2. Absolute accuracy is about +/- 0.5 for ε _average values 50 to 100 and absolute values about +/- 2.0.

Here, the birefringence value of component (B) of the medium according to the invention is measured on nematic phase at 20 ° C. and at a temperature 4 ° below the clearing point. If the medium is not nematically stable at either or both of these temperatures or at least cannot be subcooled to this temperature on the nematic phase, then the birefringence of the mixture is as described above for the determination of dielectric anisotropy. Extrapolate from the corresponding nematic host mixture.

Threshold voltage is herein an optical threshold and is indicated for a relative contrast (V ₁₀ ) of 10%. The mid-gray voltage and saturation voltage are likewise optically determined and displayed for 50% and 90% relative contrast, respectively. The reference amounts and characteristic values of the electro-optical characteristic lines of the various media shown herein are typically voltage (V ₁₀ ), and in special cases voltage (V ₇₀ ), where the characteristic lines are initially at a value of 70% relative contrast. Reached). If a capacitance threshold voltage (V ₀ ) or a voltage (V ₁₀₀ ) when reaching 100% relative contrast, also known as the Freedericks threshold, is indicated, this is stated explicitly.

The medium was introduced into a test cell with an interdigital electrode. The layer thickness of the test cell was usually about 10 μm. The width of the electrode was 10 μm, and the distance between adjacent electrodes was also 10 μm. The electro-optical characteristic line was determined at a temperature 2 ° C. above the characteristic temperature of the individual medium. While introducing the medium into the cell, a slight increase in the clearing point was observed in some cases. This effect can be explained by the specific stabilization of the nematic phase in this layer. The clearing point increase was in some cases from 0.5 ° to about 0.7 °. In some rare cases, a deviation of about 2 ° to 4 ° may occur. In the case of a medium in which the characteristic temperature of the cell is different from the bulk characteristic temperature, the characteristic temperature (transparent point) in the cell is used for characterization.

The wavelength of light is assumed to be 400 to 800 nm, preferably 555 nm.

In the present specification, particularly in the examples described below, the structure of the compound is indicated by abbreviation. The meanings of the individual abbreviations are set forth in Tables A and B below. All groups C _n H _{2n + 1} and C _m H _{2m + 1} are straight chain alkyl groups having n and m C atoms, respectively. Table B is self-explanatory because in each case the complete abbreviation for the chemical formula of the homogeneous compound is indicated. In Table A, only abbreviations for the core structures of the compound types are listed. The abbreviations for the individual compounds consist of the abbreviations for the groups R ¹ , R ² , L ¹ and L ² connected by appropriate abbreviations for the core of the compound and-respectively, according to the table below.

Mesogenic media according to the present application preferably include:

4 or more, preferably 6 or more, compounds selected from the group consisting of the compounds of Tables A and B and / or

At least five compounds selected from the group consisting of the compounds of Table B and / or

At least two compounds selected from the group consisting of the compounds of Table A.

The media according to the invention may comprise small amounts of one or more further compounds as stabilizers or for adjusting the specific resistance, if necessary. They preferably include one or more stabilizers selected from the list of compounds in Table C below.

을 갖는다.Typical compounds that can be used to adjust specific resistance are

Has

The examples described below illustrate the invention without limiting in any way. These demonstrate to those skilled in the art that properties and in particular combinations of properties can be achieved by means of the invention.

Example 1 and Comparative Examples 1a to 1d

Comparative Example 1a

An achiral liquid crystal mixture AM-1 having the following composition was prepared and investigated.

This liquid crystal mixture was introduced into a test cell and examined for its electro-optical properties at a temperature of 7.7 ° C. (5 ° higher than the transparency point) and over a temperature of 6.2 to 10.7 ° C.

The test cell used had comb-shaped electrodes on only one of the two substrates. An electro-optical test cell with a light-switching element containing a liquid crystal mixture was prepared. The substrates were made of glass. Substrates without alignment layers and substrates without passivation layers were used. The electrode structure consisted of intermeshing comb electrodes. The distance between the electrodes was 10 μm and the widths of the electrodes were 10 μm. The layer thickness of the electrodes was about 100 nm. The electrodes were all located in a common plane. The layer thickness of the modulation medium was about 10 μm.

A first polarizer was used in front of the cell and a second polarizer was used as an analyzer behind the cell. The absorption axes of the two polarizers were formed at an angle of 90 ° to each other. The angle between the maximum absorption axis of the polarizer and the field component in the display plane was 45 ° in each case. Voltage / transmission characteristic lines were measured using a DMS 703 electro-optical measuring station from Autronic-Melchers, Karlsruhe, Germany. For vertical observations, curves are obtained as are typical for cells with electrically controlled birefringence (eg, ECP).

As the temperature increases above the clearing point of the medium, the characteristic voltage monotonously increases. At 7.7 ° C., V ₇₀ is 45V. The results are shown in Table 1 below. Table 1 relates to the characteristic voltages of the various examples.

footnote:

BC ^* HC: B (OC) 2C ^* HC-3

PPX ^* : (10PZPZ) 2X ^*

n.d .: not measured

dV ₇₀ / dT: [V ₇₀ (T _{characteristic} + 3 °) -V ₇₀ (T _{characteristic} + 1 °) / (2 °)]

dV ^* ₇₀ / dT: [V ₇₀ (T _{characteristic} + 3 °) -V ₇₀ (T _{characteristic} + 1 °) / V ₇₀ (T _{characteristic} + 2 °)? (2 °)]

§: value at T _{characteristic} + 0.5 °

Example 1

A mixture consisting of 97% of the achiral liquid crystal mixture AM-1 of Comparative Example 1a and 3% of the chiral compound B (OC) 2 C ^* HC-3 was prepared and investigated. Chiral compounds of the A type (in the MLC-6828) in 20 ℃ + 137㎛ ^-1 and has a HTP of + ^-1 104㎛ in MLC-6260.

The mixture has a blue phase over a range of about 2 ° with the following phase sequence. N ^* 11.5 ° C. BP 13.5 ° C. I.

The mixture is introduced into a test cell as described in Comparative Example 1a and investigated as described. Specifically, their electro-optical properties are investigated at temperatures above their characteristic temperature. The results compared with Comparative Example 1a are shown in Table 1 below.

As can be seen from this table, the characteristic voltage V ₇₀ of the liquid crystal switching element of Example 1 is somewhat higher than the comparative example 1a at the corresponding temperature at a temperature closer than the characteristic temperature. The characteristic voltage of the liquid crystal switching element of Example 1 monotonously increases with increasing temperature as in Comparative Example 1a. However, the increase in the characteristic voltage of the liquid crystal switching element of Example 1 is initially much smaller than that of Comparative Example 1a, so that the two switching elements exhibit the same voltage V ₇₀ at a temperature of only 1.5 ° or more above their reference temperature. The temperature dependence at a temperature 2 ° above each characteristic temperature is reduced from more than 25% to less than 20% in the comparison of the light modulation element of Comparative Example 1a and the light modulation element of Example 1. At temperatures 0.5 ° C. above the characteristic temperature, the relative temperature dependence (dV ^* ₇₀ (/ V ₇₀ ) / dT) of the characteristic voltages of the present application is 9% / ° and the relative temperature dependence of the characteristic voltages at temperatures 2 ° C. above the characteristic temperature. (dV ^* ₇₀ (/ V ₇₀ ) / dT) is 45% / °.

For the mixture of Example 1 and Comparative Example 1a, cells with an electrode distance of 15 μm and an electrode width of 10 μm were further investigated. The results are shown in Table 2 below.

Footnotes: See Table 1.

BC ^* HC: B (OC) 2C ^* HC-3

§: value at T _{characteristic} + 0.5 °

The electrode distance in the cells used was exceptionally 15 μm in Table 2 herein.

Comparative Examples 1b to 1d

In Comparative Examples 1b to 1d, an achiral modulation medium was used as in Comparative Example 1a in contrast to Example 1. However, a modulation medium having a composition different from that of Comparative Example 1a was used herein.

Comparative Example 1b

A mixture having the following composition and the following properties was prepared and investigated.

The results are shown in Table 2.

Comparative Example 1c

A mixture having the following composition and the following properties was prepared and investigated.

The results are shown in Table 2.

Comparative Example 1d

A mixture having the following composition and the following properties was prepared and investigated.

The results are shown in Table 2.

As in Example 1 and Comparative Example 1a, the medium of Comparative Examples 1b to 1d was irradiated in a cell having an electrode distance of 15 μm and an electrode width of 10 μm. The results are shown in Table 2.

As can be seen in Table 2, the temperature dependence of the relative characteristic voltage (V ₇₀ ) was only 9% in Example 1, while in all four comparative examples it was substantially the same about 25%.

Examples 2a to 2d and Comparative Example 2

Comparative Example 2

First, an achiral liquid crystal mixture AM-2 having the following composition was prepared and investigated.

Example 2a

A mixture consisting of 90% of the achiral liquid crystal mixture AM-2 of Comparative Example 2 and 10% of the chiral compound B (OC) 2 C ^* HC-3 was prepared and investigated. This mixture has a characteristic temperature of 22.5 ° C. but 24.4 ° C. in the cell, which is assumed to be the characteristic temperature in this example. The temperature dependence of the voltage (V ₇₀ ) is shown in the table below (Table 3).

As can be seen in this table (Table 3), the characteristic voltage (V ₇₀ ) of the cell containing this doped mixture does not increase as the temperature increases, as in Comparative Examples 1a and 1, Instead it initially decreases with increasing temperature, then minimizes at about −11.6 ° C. and then rises again as the temperature increases further. According to this application, the temperature of 11.6 ° C. is referred to as the characteristic temperature because the characteristic voltage passes through a minimum value. At a temperature of about +/- 3 ° around this temperature (i.e., T _{characteristic} = -11.6 ° C), the temperature dependence (dV ^* ₇₀ / dT) actually disappears. That is, about 0 V / °.

The phase range of the blue phase pointed out herein is -19.3 to 13 ° C. The voltage reaches only 156V at low temperatures. That is, less than twice the minimum voltage value of 80V. The lower limit of the temperature range is the temperature at which the electro-optical effect can first be used. This can be measured from the observed response time. At 13 ° C., a voltage of 164 V is reached which is somewhat higher than twice the minimum voltage value.

When specifying an upper limit, as in the case for the lower limit, interpolation to a value having an accuracy of less than 1 ° is omitted.

Example 2b

85% of the achiral liquid crystal mixture AM-2 of Example 1 was used together with 15% of the dopant mixture DM-1 having the following composition.

Footnotes: see Table 1

Apart from one exception, the chiral compounds used in the dopant mixture DM-1 all have high positive values of HTP in the reference mixture having the indicated composition.

의 페놀 0.1%과 혼합하고, 시험 셀 내로 도입시키고, 비교예 1에 기술된 바와 같이 조사하였다. 구체적으로, 그의 전기-광학적 특성을 그의 특성 온도 이상의 다양한 온도에서 측정한다. 실시예 2a와 비교한 결과를 표 4 및 5에 제시한다.In the resulting modulation medium, no clearing point or transition to the blue phase could be measured under the microscope at temperatures below -20 ° C. Formulating a mixture of 85% AM-2 and 15% DM-1

Was mixed with 0.1% of phenol and introduced into the test cell and investigated as described in Comparative Example 1. Specifically, their electro-optical properties are measured at various temperatures above their characteristic temperature. The results in comparison to Example 2a are shown in Tables 4 and 5.

As can be seen in this table (Table 4), the characteristic voltage (V ₇₀ ) of the cell containing this doped mixture is practically independent of temperature in the temperature range of -11.4 to -5.6 ° C.

As in Example 2a, V ₇₀ initially decreases with increasing temperature, then only increases again with further temperature increase. The minimum value of V ₇₀ is about -8.5 ° C. In the temperature range of about +/- 2 ° C. of this reference temperature, the temperature dependence of the characteristic voltage (dV ₇₀ / dT) actually disappears completely again (compare Table 5 below).

Footnotes: see Table 1

ΔV ₇₀ / ΔT (T): [V ₇₀ (T + 1 °) -V ₇₀ (T-1 °) / (2 °)]

ΔV ^* ₇₀ / ΔT (T): [V ₇₀ (T + 1 °) -V ₇₀ (T-1 °) / (V ₇₀ (T)? (2 °)]

§: temperature range in this embodiment extending only one side

Example 2c

85% of the liquid crystal mixture AM-2 of Comparative Example 2 was again mixed with 15% of the dopant mixture as in Example 2b. However, here, a dopant mixture DM-2 having the following composition was used.

Footnotes: see Table 1

Chiral compounds used in the dopant mixture DM-2 have HTP values that increase with increasing temperature in the reference mixture. The resulting mixture has a characteristic temperature.

A mixture consisting of 85% AM-2 and 15% DM-2 was mixed with 0.1% phenol used in Example 2b, introduced into a test cell and investigated as described in Comparative Example 1a. Specifically, their electro-optical properties are measured at various temperatures above their characteristic temperature. Table 1 shows the results compared with Comparative Example 1a and Example 1.

Example 2d

Chiral compound (1OPZPZ) 2X ^* 10% was added to the mixture AM-2 of Comparative Example 4.

No blue phase could be directly observed in the resulting mixture. From the electro-optic data a phase transition of -5 to 9 ° C. was induced. The characteristic temperature assumed in this example was exceptionally 9 ° C. The results are shown in the table below (Table 6), which is thus included in Table 1 for comparison.

Footnotes: see Table 1

Examples 3a to 3f and Comparative Example 3

Comparative Example 3

As an achiral starting mixture, a mixture AM-3 having the following composition was prepared.

This mixture was investigated as described above. The characteristic temperature was 60 degreeC. The results are shown in Table 7.

Examples 3a-3c

As an alternative, 3%, 5% or 7% of the chiral compound B (OC) 2C ^* HC-3 used in Example 1 was added to the mixture AM-3 of Comparative Example 3 (Comparative Examples 3a, 3b and 3c, respectively). Added. The resulting mixture phase shifted to the blue phase at about 24 ° C., 36 ° C. and 46 ° C., respectively. The characteristic temperatures assumed in this example were 24.3 ° C, 36.3 ° C and 45.9 ° C, respectively. The results are shown in Table 7 below, and the results of Example 3B are thus included in Table 1.

Footnotes: see Table 1

§:

dV ₇₀ / dT: [V ₇₀ (T _{characteristic} + 2.5 °) -V ₇₀ (T _{characteristic} + 1.5 °) / (1 °)]

dV ^* ₇₀ / dT: [V ₇₀ (T _{characteristic} + 2.5 °) -V ₇₀ (T _{characteristic} + 1.5 °) / V ₇₀ (T _{characteristic} + 1 °)? (1 °)]

Examples 3d to 3f

The starting achiral mixture used was again used in the examples with the mixture AM-3 of 3a to 3c.

Chiral compound B (OC) 2 C ^* HC-3 (used in Example 1) 10%, 13% or 16% was added to this mixture (AM-3). The resulting mixture (Examples 3d, 3e and 3f, respectively) is phase shifted from the cholesteric phase to the blue phase at 6 ° C. or characterized at temperatures of 1 ° C. (Example 3e) and 0.3 ° C. (Example 3f). Has the minimum value of the characteristic line of voltage. The results are shown in the table below (Table 8).

Footnotes: see Table 1

*: It was not possible to observe the blue phase.

Claims (29)

One or more substrates, Electrode device, One or more polarizing elements, and An electro-optical light modulation device comprising a modulation medium, The optical modulation element is operated at a temperature at which the modulation medium in the unaddressed state is optically isotropic, The mesogenic modulation medium comprises a chiral component (component (A)) consisting of one or more chiral compounds, Wherein the mesogenic modulation medium is operated at a temperature at which the light modulation element has a blue phase, or the mesogenic modulation medium is operated at a temperature at which the light modulation element is isotropically present. Optical light modulation device. The method of claim 1, An electro-optical light modulation element, characterized in that the electrode device is capable of generating an electric field having a component parallel to the surface of the mesogenic modulation medium. The method of claim 1, An electro-optical light modulation element, characterized in that the mesogenic modulation medium has a blue phase. delete The method of claim 1, An electro-optical light modulation element, characterized in that the mesogenic modulation medium comprises an achiral component (component (B)) consisting of one or more achiral compounds. The method of claim 1, The relative temperature dependence of the characteristic voltage (dV ^* ₁₀ / dT) on the 10% relative contrast (V ₁₀ ) of the modulation medium is within a range of ± 1 ° at a temperature 2 ° above the characteristic temperature (T _{characteristic} ). At 30% / ° or less, electro-optical light modulation device. The method of claim 6, An electro-optical light modulation element, characterized in that the relative temperature dependence (dV ^* ₁₀ / dT) is 23% / ° or less. The method of claim 1, An electro-optical light modulation element, characterized in that the characteristic voltage for 10% relative contrast (V ₁₀ ) is 80 V or less at a temperature 2 ° above the characteristic temperature (T _{characteristic} ) of the modulation medium in the cell. The method of claim 1, An electro-optical light modulation element, characterized in that the mesogenic modulation medium comprises a chiral component (component (A)) consisting of two or more chiral compounds. The method of claim 9, An electro-optic light modulation element, wherein all chiral compounds of component (A) have the same sign of helical twisting power (HTP) at 20 ° C. in a reference mixture. The method of claim 9, An electro-optical light modulation element, characterized in that the HTP of at least one chiral compound of component (A) is at least 10 μm ⁻¹ at 20 ° C. in the reference mixture. delete The method of claim 1, An electro-optical light modulation element, characterized in that the dielectric susceptibility (ε _average ) of the modulation medium is at least 40 at a temperature higher than the transition temperature from the blue phase or the cholesteric phase to the isotropic phase. The method of claim 1, An electro-optical light modulation element, characterized in that the optical anisotropy at a temperature 4 ° lower than the transition temperature from the cholesteric phase to the isotropic phase is at least 0.050. An electro-optical display comprising at least one electro-optical light modulation element according to any one of claims 1 to 3, 5 to 11, 13 and 14. 16. The method of claim 15, An electro-optical display, characterized by being addressed by an active matrix. An electro-optic display system containing at least one electro-optical display according to claim 15. The method of claim 17, An electro-optic display system, which can be used as a television screen, computer monitor, or both. The method according to any one of claims 1 to 3, 5 to 11, 13 and 14, Electro-optical light modulation device for display of information. delete The method of claim 17, Electro-optical display system for the display of video signals or digital signals. A mesogenic modulation medium for use in an electro-optical light modulation element, characterized by having an optical isotropy at a temperature of 0 to 80 ° C. 23. The method of claim 22, A mesogenic modulation medium comprising a chiral component (component (A)) consisting of one or more chiral compounds. 24. The method of claim 23, A mesogenic modulation medium comprising an achiral component (component (B)) consisting of one or more achiral compounds. delete delete The method according to any one of claims 22 to 24, Mesogenic modulation medium, characterized in that having a characteristic temperature of 0 to 60 ℃. The method according to any one of claims 22 to 24, A mesogenic modulation medium, characterized in that the blue phase has a temperature range of at least 5 °. 29. The method of claim 28, Mesogenic modulation medium, characterized in that the blue phase has a temperature range of 10 ° or more.